uncons.swift

extension Sliceable {
  public func uncons() -> (Generator.Element, SubSlice)? {
    return first.map { ($0, dropFirst(self)) }
  }
  
  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let a = maybeNext(), b = maybeNext() {
      return (a, b, self[i..<endIndex])
    }
    return nil
  }
  
  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let a = maybeNext(), b = maybeNext(), c = maybeNext() {
      return (a, b, c, self[i..<endIndex])
    }
    return nil
  }
  
  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let a = maybeNext(), b = maybeNext(), c = maybeNext(), d = maybeNext() {
      return (a, b, c, d, self[i..<endIndex])
    }
    return nil
  }

  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let
      a = maybeNext(),
      b = maybeNext(),
      c = maybeNext(),
      d = maybeNext(),
      e = maybeNext() {
        return (a, b, c, d, e, self[i..<endIndex])
    }
    return nil
  }
  
  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let
      a = maybeNext(),
      b = maybeNext(),
      c = maybeNext(),
      d = maybeNext(),
      e = maybeNext(),
      f = maybeNext() {
        return (a, b, c, d, e, f, self[i..<endIndex])
    }
    return nil
  }
  
  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let
      a = maybeNext(),
      b = maybeNext(),
      c = maybeNext(),
      d = maybeNext(),
      e = maybeNext(),
      f = maybeNext(),
      g = maybeNext() {
        return (a, b, c, d, e, f, g, self[i..<endIndex])
    }
    return nil
  }
  
  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let
      a = maybeNext(),
      b = maybeNext(),
      c = maybeNext(),
      d = maybeNext(),
      e = maybeNext(),
      f = maybeNext(),
      g = maybeNext(),
      h = maybeNext() {
        return (a, b, c, d, e, f, g, h, self[i..<endIndex])
    }
    return nil
  }
  
  public func uncons() -> (
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    Generator.Element,
    SubSlice)? {
    var i = startIndex
    
    let maybeNext: () -> Generator.Element? = { (i == self.endIndex ? nil : self[i++]) }
    
    if let
      a = maybeNext(),
      b = maybeNext(),
      c = maybeNext(),
      d = maybeNext(),
      e = maybeNext(),
      f = maybeNext(),
      g = maybeNext(),
      h = maybeNext(),
      j = maybeNext() {
        return (a, b, c, d, e, f, g, h, j, self[i..<endIndex])
    }
    return nil
  }
}

let list = [Int](0..<8)


list.uncons().map { // (0, [1, 2, 3, 4, 5, 6, 7])
  (a, b) in (a, b)
}
list.uncons().map { // (0, 1, [2, 3, 4, 5, 6, 7])
  (a, b, c) in (a, b, c)
}
list.uncons().map { // (0, 1, 2, [3, 4, 5, 6, 7])
  (a, b, c, d) in (a, b, c, d)
}
list.uncons().map { // (0, 1, 2, 3, [4, 5, 6, 7])
  (a, b, c, d, e) in (a, b, c, d, e)
}
list.uncons().map { // (0, 1, 2, 3, 4, [5, 6, 7])
  (a, b, c, d, e, f) in (a, b, c, d, e, f)
}
list.uncons().map { // (0, 1, 2, 3, 4, 5, [6, 7])
  (a, b, c, d, e, f, g) in (a, b, c, d, e, f, g)
}
list.uncons().map { // (0, 1, 2, 3, 4, 5, 6, [7])
  (a, b, c, d, e, f, g, h) in (a, b, c, d, e, f, g, h)
}
list.uncons().map { // (0, 1, 2, 3, 4, 5, 6, 7, [])
  (a, b, c, d, e, f, g, h, i) in (a, b, c, d, e, f, g, h, i)
}
list.uncons().map { // nil
  (a, b, c, d, e, f, g, h, i, j) in (a, b, c, d, e, f, g, h, i, j)
}